Unsymmetrical cyanines



Patented Mar. 15, 1949 UN SYMMETRICAL CYANIN ES Douglas William Stammers, Blackley,

Man-

chester, England, assignor to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application June 28, 1945, Serial No. 602,169. In Great Britain July 17, 1944 Claims. 1

This invention relates to the manufacture of new unsymmetrical cyanines and related compounds, and in particular to such of these compounds as contain at least one 1:5-phenanthroline nucleus. The new compounds are applicable as photographic sensitisers, and this application likewise falls within the present invention.

The historical development of the chemistry of cyanine compounds, largely of interest as photographic chemicals and dyestuffs and often known as cyanine dyes, has not been such as to facilitate the naming of the compounds in question. As a consequence divers schemes of nomenclature have found employment in varying degree. Also in the matter of definition difi'ioulties arise when it is aimed to embrace the classes of cyanines and compounds chemically akin thereto now known. Reference is made to the article Cyanine dyes in Thorpes Dictionary of Applied Chemistry, fourth edition, vol. III, especially pages 530 and 531, where it is pointed out that various types of related compounds are sometimes described together with the cyanines as there defined. Compounds which may be seen in the light of present day knowledge to be logically related together by common features of chemical constitution and properties comprise, inter alia:

(l) 4:4-cyanines which compounds possess two heterocyclic nuclei containing at least one nitrogen atom each, of which one is tertiary while the other is quaternary, that is, forms part of a quaternary salt, the heterocyclic nuclei being joined by an odd number of methine linkages. According as the number of methine linkages is one, three, five or more, the compounds are referred to as being monomethine, trimethine, pentamethine, et cetera, compounds.

(2) 2:.4- cyanines (including iso cyanines). These compounds, as indicated by the numerical prefix, only difier from the aforesaid 4:4- cyanines, in respect of the positions, relative to the nitrogen atoms mentioned, at which the chain of methine linkages is attached to the heterocyclic nuclei.

(3) 2:2'-cyanines (including pseudocyanines) to which what has been already said under (1) 4:4'-cyanines is equally pertinent. All the above cyanines, i. e. 4:4'-, 2:4'- and 2:2 are characterised by containing in their structure a conjugation system having the following configuration:

This conjuga- 2 tion system is also known as a resonance system because theory postulates the dynamic oscillation of the structure, with alternation of the single and double bonds in the carbon chain intermediate between the two nitrogen atoms, otherwise expressed as an alternation of the positive electrical charge distribution along the methine chain between the aforesaid nitrogen atoms. The present invention is not concerned with the truth or untruth of this theory which is quoted by way of some explanation of these characteristic conjugation systems which represent attempts found in the scientific literature to mirror the chemical properties of the compounds under discussion.

(4) Merocyanines which are distinguished by possessing a heterocyclic nucleus containing a tertiary nitrogen atom which nucleus is linked by a chain of an even number of methine groups to a cyclic or acyclic hetero residue wherein the carbon atom at the end of the aforesaid chain has next to it a carbonyl group. Such compounds exhibit as a feature of their structure the following resonating conjugate system:

a They are made by the condensation of a quaternary salt of a heterocyclic nitrogen compound, carrying, e. g. an anilino-vinyl group in the aor 'y-position, with a cyclic or acyclic compound compound containing a methylene group adjacent to, and activated by, a carbonyl group.

(5) Compounds related to the merocyanines which can be made by employing instead of the cyclic or acyclic compound, containing a methylene group adjacent to a carbonyl group, mentioned under (4), such a compound where'the carbonyl group is replaced by a CH=C 1 grouping, which grouping likewise activates the methylene group. In these compounds is found a very similar resonating system to that of th merocyanines, namely: I

(6) Cyanosubstituted cyanine bases which can be made by the condensation of a quaternary salt of a heterocyclic nitrogen compound carying e. g. a halogen substituent in the uor y-position, with a heterocyclic nitrogen compound bearing .a cyanomethyl group in the 01- or 7-p0Sition to the may be obtained the following modes of preparation are quoted as examples of general methods.

2-methylmercapto-1 :-phenanthroline methyl p-toluene sulphonate is obtainable by oxidising 1:5-phenanthroline methosulphate to I-methyl- 2-phenanthrolone, converting with P285 to 1- methyl-2-thiophenanthrolone (M. P. 268 C.) and heating with methyl p-toluene sulphonate. The analogon 2-methylmercapto-1:S-phenanthroline ethyl p-toluene sulphonate can be made in a similar manner from 1-ethyl 2-thiophenanthrolone (M. P. 204 C.), itself got by oxidising 1 5-phenanthroline ethosulphate.

2-methyl-4-furylthiazole ethiodide (M. P. 140- 141 C.) can be made by brominating furyl methyl ketone (the preparation of this latter is described in the Berichte der Deutschen Chemischen Gesellschaft 1900, vol. 33, page 493), condensing the resulting furyl bromomethyl ketone with thioacetamide and converting the Z-methyl- -furylthiazole to a quaternary salt by treatment with ethyl iodide.

Z-cyanomethyl-G-methyl-l:5 phenanthroline can be obtained from the oxime of 6-methyl-2- phenanthrolylpyruric acid by applying heat as described in respect of the corresponding quinolyl compound by Borsche and Manteufiel in the Annalen der Chemie 1936, vol. 526, page 36.

2-,6-ethylmercaptovinyl 6 phenylbenzoxazole methyl p-toluene sulphonate (M. P. 211 C.) may be produced by converting 2-methyl-6-phenylbenzoxazole to a quaternary salt by heating with methyl p-toluene sulphonate, and then condensing the quaternary salt with ethyl trithioorthoformate.

2 5-acetylanilinobutadienyl(1' :3) -6 methyllz5-phenanthroline methiodide is made by heating 2 6-dimethyl-1 :S-phenanthioline methiodide with ,B-anilinoacrolein hydrochloride in acetic anhydride. The corresponding ethiodide is obtainable in like manner from 2:6-dimethyl-1z5- phenanthroline ethiodide.

2-,B-actylanilinovinyl-G-methyl-1:5 phenanthroline ethiodide (M. P. 225-227 C.) is got by heating with acetic anhydride (containing a little triethylamine) the compound 2-p-aminovinyl-6- methyl-1:B-phenanthroline ethiodide. The latter can be obtained by condensing 2:6-dimethyl- 1:5-phenanthroline with diphenylformamidine.

2-p-ethylmercaptovinyl 1:5 phenanthroline methiodide (M. P. 228 C.) can be made by heating 2-methyl-1:5-phenanthroline methyl p-tolulene sulphonate with ethyl trithioorthoformate in acetic anhydride.

2(6 methyl 6 ethylmercapto butadienyl (1:3))-6-methyl-1:5 phenanthroline ethiodide (M. P. 240 C.) is obtainable by treating 1-ethyl- 2-.Bfl-diacetylallylidene-B-methyl 1:2 dihydro- 1:5-phenanthroline (vide Example 12) in methanol and ethyl mercaptan with dry gaseous hydrogen chloride. The solid obtained an evaporating the reaction mixture to dryness contains 2 (e-methyl-a-ethylmercapto butadienyl 1 :3) 6 methyl 1:5 phenanthroline ethyl chloride. This is converted to the corresponding ethiodide by treating it in aqueous medium with potassium iodide. The ethiodide is separated from byproducts by crystallisation from methanol.

The condensation effected between the first and second components of the cyanine according to this invention may be accelerated by warmth. It is likewise assisted by and proceeds readily in the presence of acid-binding agents, e. g. sodium ethylate, sodium acetate or sodium carbonate.

Preferably, however, an organic base may often be used, particularly one forming with the anion of the quaternary salt (first component) a salt possessing a dissociation constant substantially greater than that of the corresponding pyridine salt. Such a base is triethylamine or triethanolamine. N-methylpiperidine will also serve. Advantageously the quantity of base is in excess of that corresponding stoichiometrically with the amount of acid to be taken up, viz. the one equivalent proportion of acid which is eliminated in connection with the condensation together of one molecular proportion each of the two components to form the cyanine. The excess of base adopted can conveniently be twice or thrice the theoretical amount. It is not seldom advisable for ease of handling to bring about the condensation in the presence of a solvent or diluent. Such diluent can be, for instance, anhydrous ethanol or another aliphatic alcohol not containing more than four carbon atoms. Pyridine can frequently be chosen as solvent; it then sometimes serves sufliciently also as acid-binding agent.

The cyanines of the present invention which, as already indicated, contain at least one heterocyclic nitrogen nucleus being a Lil-phenanthroline residue, and may be made by the above process, are eminently suitable for use as photographic sensitisers, and photographic silver halide emulsions having such cyanines incorporated therein constitute a further feature of this invention.

The present cyanines may be used as sensitisers not only in gelatino-silver chloride but also in gelatino-silver bromide and gelatino silver bromoiodide emulsions for instance. Silver halide emulsions dispersed in carriers or binders other than gelatin may also have their sensitivity modified by these cyanines. The new cyanines may serve as components of super sensitising mixtures. The present cyanines may also constitute one or more of the constituents of a sensitising mixture such as is, for example, em-

" ployed in sensitising a silver halide emulsion to give approximately uniform sensitivity to light over a wider range of the spectrum than can usually be accomplished by means of a single sensitising compound. Such sensitising emulsions are particularly valuable for coating colour reseau printed film base (see Colour Cinematography by Adrian Klein, 1936, p. 138) in the manufacture of the so-called additive sort of colour photographic films. The present cyanines, moreover, afiord compounds adapted to sensitise photographic emulsions made use of in the manufacture of multi-layer "subtractive colour photographic elements (cf. Adrian Klein, ibid., p. 154) Variable contrast emulsions comprising sensitised and unsensitised emulsion mixtures, or mixed emulsions containing grains sensitised to different regions of the spectrum can also be prepared with the aid of the cyanines of this invention.

The present cyanines may be incorporated in the photographic emulsion to be sensitised by any process known in the art. For example, solutions of the new cyanines (containing 5-1000 mg., say) in a solvent compatible with the emulsion, e. g. methanol or acetone, may be mixed slowly with 1 litre of molten washed gelatinosilver halide emulsion (containing 15-40 gm. of silver halide) until the cyanine is uniformly dis trlbuted throughout the emulsion. Or else, for instance, a photographic emulsion with which a support, e. g. a glass plate or film base, has been coated, may be sensitised by bathing the coated support in a solution of the cyanine. Solutions in .aqueous methanol or acetone with a water content of 10-70% by volume areespecially suitable.

The-following examples are by way of illustrating, but not limiting, the invention.

Example 1 5.15 grams of d-anilinovinylquinoline ethiodide, 3.6 =ccs...of acetic anhydride and /2 cc. of triethylamine are heated together at 110 C. for 5 minutes. The melt is cooled and diluted with. 330 cos. of ethanol. 4.6 grams of 2:6dimethyl-1:5- phenanthroline methiodide are added. The mixture is stirred at 80 C. .for 20 minutes, 5.0 cos. of triethylamine beingallowed to drip in during the first.5 of these minutes, and then cooled to C. The compound (1 6-dimethyl-1 :5--phenanthro line-.2) (l-ethylquinolinel) -trimethine cyanine iodide, precipitated during 2 hours, is filtered off, washed with 40 cos. of ice-cold ethanol and recrystallised twice from boiling methanol, from which solvent it separates in the form of bright green needles with a metallic reflex, melting at 289-290" C. with decomposition. The new cyanine confers a vbandof sensitivity between 650 and 720 m .on a silver bromiodide emulsion, with a maximum at about 690m Example 2 1 gram of 2:6-dimethyl-1:5--phenanthroline ethiodide is boiled under reflux in .60 cos. of ethanol containing 1.20 cos. of triethylamine until solution of'the quaternary salt is complete. 0.62 gram of 2-13-acetylanilinovinylbenzoxazole ethiodide is added and the mixture boiled under reflux with stirring for a further 2 minutes. The temperature is then brought down to 5 C., and the new cyanine (1:G-dimethyl-l:5-phenanthroline-2) (l-ethylbenzoxazole-Z)-trimethine cyanine iodide, which separates, filtered oii, washed with ice-cold ethanol, and twice recrystallised from ethanol. It forms deep red felted needles melting at273-4 C. The new compound will extend the sensitivity of .a silver bromiodide emulsion to about 650 m with a broad maximum at about 600 m l.

Example 3 .A mixture of 1.0 gm. of 2-ani1inoviny1-6- methyl-1:5-phenanthroline ethiodide, 0.4 cc. of acetic anhydride and 0.4: cc. of triethylamine is heated at 130 C. for 3 minutes under reflux. After cooling, 10 cos. of ethanol are added, followed'by 0.675 gm. of 2:3z3-trimethylindolenine ethiodide and 1.0 cc. of triethylamine. The mixture {is boiled gently under reflux for 30 minutes, cooledfor 2 hours in melting ice, and the separated cyanine (l-ethyl-B-methyl-l:S-phenanthroiine-Z) (1-ethyl-3 3-dimethylindolenine-2 .trimethine cyanine iodide filtered off. After recrystallisation -from methanol it forms green felted needles melting at 281-282" C. with decom position. The sensitivity or a silver bromiodide emulsion is increased strongly by this new cyanine up to about 680 m with a broad maximum between 620 and 650 m Example 4 0.7 gram of 2:6-dimethyl-1:S-phenanthroline ethiodide and 0.75 gm. of 2-methylmercapto- 2'zl'z-naphthathiazole thiazole are dissolved in 35 cos. of boiling ethanol; 0.8 cc. of triethylamine i'sadded. The mixture is heated at 90 C. for 1 'hourwithstirring, cooled, and the new cyanine,

.fina'lly twice recrystallised from hot methanol.

8 .(1--.ethyl -6 -.methyl -.1:5 -.phenanthro1ine 2) (l-ethyl-Z-1'-naphthathiazole-2) monomethine cyanine iodide, filtered off. After recrystallisation irom methanol it appears as small orange needles meltingat 281 '0.

Example 5 0.8 gram of 2-.methylmercapto-l 5-phenanthroline .methyl p-toluene sulphonate are dissolved by warming in 15100. of ethanol and 1.06 gm. of lepidine ethiodide added, followed by 1.5 cc. of triethylamine. After being heated under reflux for 10 minutes, the mixture is cooled and the ,neW cyanine, (1-methyl 1:5 phenanthroline-il) '(1- ethyl-quinoline-4)-monomethine cyanine iodide, filtered off, washed with .cold methanol, and finally, twice recrystallised from methanol. It separates. as dark green felted needles, melting at 261 C.

Example 6 1.0 gram of vbsnzthiazoline and 0.792 gms. of methyl-p-toluene sulphonate are fused together at C. for 30 minutes. The product which is z-c-methylmercapto 6 methylvinylmercaptobenzthiazole ethyl- .p-toluene sulphonate, is dissolved in 10 cos. of ethanol by warming. To this solution, 1.548 gm. of 21.6-dimethyl-1 :5-phenanthroline ethiodide are added followed by 1.8 cos. of triethylamine. The mixture is heated under reflux for ,10 -minutes and then cooled in-melting ice for one hour. The new-cyanine, (l-ethyl-fi-methyl- 1:5-phenanthroline 2-) (1 ethylbenzthiazole 2) mesomethyltrimethine cyanine iodide, is filtered ofi. It is purified by washing with cold methanol, water, andufinally by recrystallisation from methanol, forming small dark prisms having a metallic reflex andmelting at 268-9 C.

Example 8 0.9 34 gram of 243-ethylmercaptovinyl-fiphenylbenzoxazole methyl p-toluene sulphonate .and 0.728 gm. of 216-dimethyl--phenanthr0- line ethiodide are stirred in 40 cos. of ethanol containing 0.8 .cc. of triethylamine at -80 85 C. for .20 .minutes. The new cyanine, (1-ethyl- G-methyl-l 5 -phenanthroline-2 (l-methyl-G- phenylbenzoxazo'le-2) -trimethine cyanine iodide, is filtered .off, washed with cold methanol and It forms long dark red needles, melting at 211 C.

Example 9 0.56.4 gram of .2-methyl-l:5-phenanthroline ethiodide, 0.75 gm. of 2-5-acety1ani1inobutadienyl-'(1":3i) -'benzthiazole ethiodide and "0.7 cc. .of triethylamine were added to 25 cos. of ethanol and the mixture heated with stirring at 65- 70 C. for -30 .minutes. vAfter cooling the new cyanine separating, namely (l-ethyll 5-phenanthroline- 2) il-ethylbenzthiazole-Z)-pentamethine cyanine iodide .is filtered off, extracted with 15 cos of boiling methanol, and twice recrystallised from methanol. The light green lustrous plate-like crystals obtained melt at 270-2l1 C.

Example 10 1.0 gram of 2-6-acetylanilinobutadienyl-(13') 6-methyl-1:fi-phenanthroline methiodide and 0.616 gm. of 2-methyl-5-furyl-thiazole ethiodide are dissolved in 6 ccs. of pyridine at 30 C. with stirring; 0.8 cc. of triethylamine are then added and the temperature of the outer bath slowly raised to 70-75 C. during 30 minutes. The mixture is cooled, diluted with 20 ccs. of ether and the new cyanine filtered off. It is (1:6-dimethyl- 1:5-phenanthro1ine-2) (l-ethyl- -furyl-thiazole- 2) -pentamethine cyanine iodide, being purified by extraction with methanol and water. It then forms a dark bluish-red powder melting at 235 C.

Example 11 0.466 gram of 2- 'cyanomethyl-6-methyl-125- phenanthroline and 0.90 gram of 2-fi-acetylanilinovinylbenzthiazole ethiodide are dissolved by warming in cos. of ethanol, and 0.3 cc. of triethylamine added. The mixture is boiled under reflux for minutes, cooled, and diluted with 30 ccs. of cold water. The new cyanine, l-cyano- 1-(6 -methylphenanthrolyl- 2) -3(1"- ethylbenzthiazolylidene- 2") propene (1), twice recrystallised from methanol forms brick-red needles melting at 249 C.

Example 12 5.0 grams of 2-;8-acetylanilinovinyl-G-methyl- Lil-phenanthroline ethiodide and 2.0 ccs. of acetylacetone in 20 ccs. of ethanol are raised to the boil and 1.65 ccs. of triethylamine added. The mixture is cooled and diluted by the gradual addition of 80 ccs. of ice cold water. The solid, namely, l-ethyl-2-fi,Bdiacetylallylidene-6-methyl-l:2-dihydro-1:5-phenanthroline, is filtered off, washed with methanol and recrystallised from benzene. It separates from benzene as deep red prisms melting at 222-3 C.

1 Example 13 0.510 gram of 24i-acetylanilinovinyl-6-methyl-1:5-phenanthroline ethiodide and 0.132 gm. of rhodanine are dissolved in 10 ccs. of ethanol containing 0.28 cc. of triethylamine. The mixture is heated at the boil under reflux for 2 minutes and the new compound filtered off from the hot solution. It is 1-ethyl-6-methyl-2- phenanthrolylidene-ethylidene rhodanine and is obtained in the form of dark green needles, with a metallic reflex and melting at 312 C., by extracting the crude compound with boiling ethanol.

Further embodiments of the invention are subjoined in briefer form, the names of the first and second components, which are to be condensed together, being quoted, together with the names of the new cyanines so obtained, and their melting points and appearance.

Example 14 Appearanceplate-like crystals Melting point -284 c.

Example 15 1st component2-methylmercaptobenzthiazole ethyl p-toluene sulphonate.

2nd component2 G-dimethyl-l B-phenanthroline ethiodide.

Cyanine-( l-ethyl- 6 -methyl- 1'15 -phenanthroline-2) (l-ethylbenzthiazole-2) -monomethine cyanine iodide.

Appearance-orange needles.

Melting point272 C.

Example 16 1st component2 -methy1mereapto- 1 5-phenanthroline methyl p-toluene sulphonate.

2nd component2-methyl-benzselenazole ethiodide.

Cyanine--( I-methyl-l 5-phenanthroline-2) (1- ethylbenzselenazole-2) monomethine cyanine iodide.

Appearancelong felted orange needles.

Melting point-283 0',

Example 17 1st component2-methylmercapto-1 :5-phenanthroline methyl p-toluene sulphonate.

2nd component2-methyl-4-furylthiazole ethiodide.

Cyanine( l-methyl-l:5-phenanthroline-2I) (lethyl-5-furylthiazole-2) monomethine cyanine iodide.

Appearance-scarlet needles.

Melting point263 C.

Example 18 2nd component2-methyl-4-furylthiazole ethiodide.

Cyanine( 1 ethyl 1:5 phenanthroline-2) (lethyl-4-furylthiazole-2) monomethine cyanine iodide.

Appearance-scarlet needles.

Melting point-262 C.

Example 20 1st component-2-methylmercapt0-l:S-phenanthroline ethyl p-toluene sulphonate.

2nd component-2:6-dimethyl-1 :5-phenanthroline ethiodide.

Cyanine--(1- ethyl G-methyl -l :5- phenanthroline-2) (l-ethyl-l:5-phenanthro1ine-2) monomethine cyanine iodide.

Appearancebrick red needles.

Melting point-+298 0.

Example 21 1st component2 methylmercapto -2':1-naphthathiazole ethiodide.

2nd component2 methyl -1 :S-phenanthroline ethiodide.

Cyanine(1 ethyl -l :5 phenanthroline 2) (1- ethyl. 2':1'- naphthathiazole-2) monomethine cyanine iodide.

Appearance-orange-red needles.

Melting point-265 C.

11' Example 22- 1st component-2-5-acetylanilinovinyl-1:3 :3-trimethyl indolenine iodide.

2nd component-2 G-dimethyl -l :5-phenanthroline. methiodide.

C yanine 1 :G-dimethyl- 1.: 5 -phenanthroline-2) (l':3:3-trimethyl indolenine-Z) trimethine cyanine iodide.

Appearance-green needles.

Melting point270-271 C.

Example 23 1st component-2.-;3-acetylanilinovinyl-1 :3:3-trimethyl indolenine iodide.

2nd component-2 :6-dimethyl -1:5-phenanthrolinev ethiodide.

Cyanine-(lethyl 6- methyl -1:5-phenanthroline-2') (1:3 3-trimethylindolenine-2) trimethine cyanine iodide.

Appearancesmall dark green. prisms.

Melting point-288 C.

Example 24 1st component--2 c ethylmercaptovinyl 1:5-

phe'nanthroline methiodide.

2nd component-2' methylbenzselenazole-ethiodide.

Cyanine(1- methyl -1:5- phenanthrolinee2); (1-

ethylbenzselenazole-Z) trimethine cyanine iodide.

Appearance-light green needles.

Melting point-293 0.

Example 25 1st component-2 ;8- ethylmercaptovin-yl 1 :5-

phenanthroline methiodida.

2nd component-N-ethylrhodanine.

Cyanine- 1 methyl-phenanthrolylidene-ethylidene) -N-ethylrhodanine.

Appearance--bluish redI needles.

Melting point312-314 C.

Example" 26.

1st component-Z- (e-methyl 6 ethylmercapto-- butadienyl- (1:3)) S-methyl -1 :5phenanthroline ethiodide.

2nd component--2methylbenzthiazole methiodide.

Cyanine--(1'-ethyl- 6 methyl -1:5-.-phenanthroline) (1 ethylbenzthiazole-2) -6-methylpentamethine cyanine iodide.

Appearance-green prisms.-

Melting point202." C.

Example. 22

' aminohutadienyl with. a different heterocyclic nitrogen compound taken from the class consisting of quaternary salts of heterocyclic nitrogen compounds containing a reactive methyl group'in one of the positions alpha and gamma to the heterocycli'c. nitrogen atom, heterocyclic nitrogen. base compounds containing a cyanomethyl. group in one of, the positions. alpha and gamma to the heterocyclicnitrogen.atom and cyclic and acyclic compounds containing a reactive. methylene group adjacent to a carbonyl radical, at least one of said heterocyclic nitrogen compounds containing a.1,5-phenanthroline nucleus containing the prescribed reactive group in the alpha position to the l-nitrogen atomthereof.

2. A process for the manufacture of unsymmetrical cyam'ne dyes: containing, at least one 1,5- phehanthroline nucleus which comprises condensing a quaternary salt of a heterocyclic nitrogen compound: containing inone of the positions. alpha and gamma to. the. heterocyclic nitrogen atom areactive group taken from the-class consisting of halogeno, alkylmercapto, aralkylmercapto, alkylmercaptovinyl, aralkylmercaptovinyl, alkylrnercaptobutadienyl, aralkylmercaptobutadienyl, N'-aryl'aminoviny1, N-arylaminobutadienyl, N-arylacylaminovinyl, and N-arylacylaminobutadienyl with a different heterocyclic nitrogen compound quaternary salt containing a reactive methylgroup inone of the positions alpha and gamma to the heterocyclic nitrogenatom, at least oneof said heterocyclic. nitrogen compounds containing a 1,5.-phenanthroline. nucleus bearing the prescribed reactive group in. the alpha positiontothe 1-nitrogen atom thereof.

3; A. process for: the manufacture of unsymmetrical cyanine dyes which comprises condensing a 1-,5-phenanthroline quaternary salt which has a reactive group in the 2-position taken from the class consisting of'halogeno, alkylmercapto, aralkylmercapto, alkylmercaptovinyl, aralkylmercaptovinyl, alkylmercpatobutadienyl, aralkylmercaptobutadienyl, N-arylaminovinyl, N- arylaminobutadienyl,..Nrarylacylaminovinyl, and N-arylacylaminobutadi'enyl groups with a heterocyclic ketomethylene compound of the. formula where A constitutes the atoms necessary to complete a 5 to 6 membered ketomethylene nucleus.

4. An unsymmetrical cyanine dye of the formula.

aralkyl groups, n is a number taken from the 7.

group consisting of 0, 1 -and.2 and Xis the negative radical of an acid.

13 14 5. A merocyanine dye of the formula alkyl and aralkyl radicals and n is a. number taken I n from the group consisting of 0, 1 and 2. DOUGLAS WILLIAM STAMMERS. o(=cH-0H= ,.o-c--- l 5 REFERENCES CITED The following references are of record in the file of this patent: wherein A constitutes the atoms necessary to complete a 1,5-phenanthro1ine nucleus, A con- UNITED STATES PATENTS stitutes the atoms necessary to complete a. 5 to 6 Number Name Date membered heterocyclic ketomethylene nucleus, R 1,939,201 Brooker Dec. 12, 1933 is a member taken from the group consisting of 1,962,123 Brooker June 12, 1934 

